class LazySingleton {
  private static instance: LazySingleton = null;

  private constructor() { }

  public static getInstance(): LazySingleton {
    if (this.instance === null) {
      this.instance = new LazySingleton()
    }
    return this.instance
  }
}

const install1 = LazySingleton.getInstance()
const install2 = LazySingleton.getInstance()
console.log(install1 === install2)